Alprostadil is used to treat erectile dysfunction (impotence) and to help diagnose certain causes of this disorder. Alprostadil is also used to improve blood flow in newborn babies with a certain genetic heart condition. This alprostadil medication guide addresses only the adult male use of this medication in erectile disorders. Alprostadil relaxes blood vessels and muscles in the penis. This increases blood flow into the penis, causing an erection. Alprostadil may also be used for purposes not listed in this medication guide.